A control apparatus, that controls driving of an AC rotary machine such as an induction motor, an induction generator, a synchronous motor, and a synchronous generator, is required to obtain electric constants such as a resistance and an inductance of the AC rotary machine. The inductance of the rotary machine that is not connected to a load machine can be measured by no-load test. However, the rotary machine connected to the load machine cannot be subjected to any no-load test. Therefore, it is conventionally required to measure the constants of the rotary machine that do not need to be subjected to any no-load test.
As disclosed on page 3 of a Patent document 1, for example, in a rotary machine constant measuring apparatus of a prior art, a single-phase AC voltage having a frequency f1 is applied between two of three-phase input terminals of an induction motor in a stopped state, an AC current flowing and an AC voltage which is applied in the induction motor are detected, an amplitude and a phase of a fundamental wave are calculated based on the detected AC current and AC voltage, and a sum of primary and secondary leakage inductances and a sum of primary and secondary winding resistances are calculated from a relationship between the calculated amplitude and phase.
In addition, as disclosed on page 4 of Patent Document 2, a sinusoidal wave modulated signal is generated by a single-phase AC excitation processing, the generated sinusoidal wave modulated signal is inputted to an inverter through a gate circuit, the inverter is then actuated, an AC motor is driven by an AC excitation voltage converted into a power by the inverter, to make AC current flow in the AC motor. Thereinafter, in a calculation processing for an effective power current Iq (means a current for effective power) and an effective power current Id (means a current for effective power), the effective power current Iq and the ineffective power current Id are calculated based on a signal sin θ, a signal −cos θ, and a U-phase motor current iu, where θ is a rotational phase of an AC excitation voltage vector as obtained by integrating a primary frequency command. Further, in a calculation processing for a combined resistance of primary and secondary resistances and a combined leakage inductance of primary and secondary combined leakage inductances, a sum of the primary and secondary leakage inductances and a sum of the primary and secondary winding resistances are calculated from the calculated effective power current Iq and ineffective power current Id, and a magnitude of the excitation voltage command.
Furthermore, as disclosed in, for example, Patent Document 3, measuring conditions are set so as to be that the command values of a primary angular frequency command and a q-axis voltage command are both zero, and that an AC signal is applied as a command value of a d-axis voltage command. If a measurement is conducted according to these measuring conditions, then any three-phase AC currents do not flow but a V-phase current and a W-phase current become in phase, and a single-phase AC current flows. Therefore, the AC motor can be kept in a stopped state without rotating the same motor. When the rotation of the AC motor is stopped, a d-axis current component flowing in the AC motor is detected, a detection value of the detected d-axis current component is analyzed according to a Fourier expansion by means of a trigonometric function based on the d-axis voltage command value, and the constants of the AC motor are calculated based on a Fourier coefficient of a fundamental wave component and the d-axis voltage command value.
Moreover, for example, Patent Document 4 discloses a induction motor constant measuring method using an inverter. In this case, a lock test is conducted using two frequencies near a slip frequency at which an induction motor actually operates, and a leakage reactance including an excitation inductance and a secondary resistance are calculated. With this method, the single-phase AC voltages having two different angular frequencies ωa and ωb near a frequency at which the induction motor operates are applied to an input terminal of the induction motor, and resistances Ra and Rb and inductances Xa and Xb that are serial impedance components when seen from a motor terminal are measured based on currents with the respective angular frequencies ωa and ωb.
Further, for example, Patent Document 5 discloses an induction motor constant measuring method capable of easily measuring respective constants of a vector control induction motor using only a winding resistance measurement and a lock test. This constant measuring method is provided for measuring the respective constants of a T-1 type equivalent circuit of the induction motor during the lock test when an excitation inductance is connected to a common contact point to a leakage inductance and a secondary resistance. With this constant measuring method, the wiring resistance measurement is conducted, and the lock test using a first frequency out of two arbitrary different frequencies are first performed to measure a resistance component R and a reactance component X of a combined impedance. The lock test is then conducted again using a second frequency to measure a resistance component R′ and a reactance component X′ of the combined impedance. These resistance components and reactance components are calculated, and this leads to measurement of the respective constants of the induction motor.
Additionally, Patent Document 6 discloses an induction motor constant measuring method including the following steps for calculating induction motor constants:
(a) applying a predetermined voltage having a first frequency to an induction motor, and measuring a magnitude of an induction motor current corresponding to the applied predetermined voltage having the first frequency, and a phase difference between the induction motor current and the applied predetermined voltage having the first frequency.
(b) applying a predetermined voltage having a second frequency different from the first frequency to the induction motor, and measuring a magnitude of an induction motor current corresponding to the applied predetermined voltage having the second frequency, and a phase difference between the induction motor current and the applied predetermined voltage having the second frequency.
(c) calculating the induction motor constants using a magnitude of the applied predetermined voltage having the first frequency, the magnitude of the induction motor current corresponding to the applied predetermined voltage having the first frequency, the phase difference between the induction motor current and the applied predetermined voltage having the first frequency, a magnitude of the applied predetermined voltage having the second frequency, the magnitude of the induction motor current corresponding to the applied predetermined voltage having the second frequency, and the phase difference between the induction motor current and the applied predetermined voltage having the second frequency.
In the prior art, the measurement is conducted twice by changing the frequency condition. On the other hand, this induction motor constant measuring method is characterized by superimposing the predetermined voltage having the first frequency and the predetermined voltage having the second frequency, and by simultaneously applying the voltages to the induction motor. Then the above-mentioned voltage application step can be completed by one measurement.
Patent document 1: Japanese patent No. 2759932;
Patent document 2: Japanese patent No. 3284602;
Patent document 3: Japanese patent No. 2929344;
Patent document 4: Japanese patent No. 3052315;
Patent document 5: Japanese patent laid-open publication No. JP-06-153568-A
Patent document 6: Japanese patent laid-open publication No. JP-2003-339198-A;
Non-patent document 1: Y. Murai et a., “Three-Phase Current-Waveform-Detection on PWM Inverters from DC Link Current-Steps”, Proceedings of IPEC-Yokohama 1995, pp. 271-275, Yokohama, Japan, April 1995.
Non-patent document 2: Citizen Watch Co., Ltd., Information Bureau, “Questionnaires on “Time Day” (June 10), and Businessperson's Sense of “Waiting Time””, http://www.citizen.co.jp/info/news.html and http://www.citizen.co.jp/release/03/0304dn/0305dn_t.htm, published on May 28, 2003.